Here's the Hojo article I mentioned above in which, at least in this article, theanine content is linked to more intensive application of fertilizers/nitrogen. As is often the case for me with Hojo I find his viewpoints interesting and generally bearing merit, whether I am in full agreement with them or not.:

There are very big difference in natural grown tea tree, organic plantation tea and plantation tea.

Natural tea should be the standard of all, since its the original form of natural growing with the natural available substances.

Organic tea can be well grown if fertilizer method is likely in a more greenish way, while the tea did growth healthily. Certain claims that organic plantations tea/vege/fruits are not as nice like the usual normal in terms of out look such as the leaves may be bitten and not as strong or big in size. But THINK another way, isn't a well grown plant should be more strong in terms of everything? Why is it being weak compare to normal plantation method, something wrong that the plant never grown healthily?

Plantation tea is the most common tea around the world, since we are in Pu Erh topic, plantation tea covers up to more than 85% in overall Yunnan, while natural grown stands the minor 15%. Its surviving enquiry is fertilizer and pesticide. Fertilizer to fulfill the basics living, pesticide to protect it from insect harm.

A Healthy grown tea tree should be able to fight or defense against pest as the tannin compounds are widely distributed in many species of plants, where they play a role in protection from predation, and perhaps also as pesticides, and in plant growth regulation.

Natural grown tea acquire this tannin like a healthy natural body immune system, while plantation tea are different in terms of growing method. Here we focus on tea plantation in Yunnan, because Japan and other countries may varies in method.

Yes, thank you. My knowledge of the underlying causes for increased theanine content is cursory. I set up a Deepdyve account to have access to the scientific/journal literature on tea. I am amazed (and excited) at how many studies are actually being done. Last night I read a study titled "Determination of amino acids in white, green, black, oolong, pu-erh teas and tea products" by Rouba Horanni and Ulrich H. Engelbracht. The study affirmed your assertion and states that, "Shading of the tea plant was employed to enhance the amount of amino acids, especially that of 1-theanine (Chu and Juneja, 1997)."

In Hojo's account (http://hojotea.com/en/posts-47/) he links to his study but the study is in Japanese. However, Hojo writes, "In 1950, Dr. Sakado discovered the substance called Theanine that produces the taste of umami which taste is somewhat like “mono sodium gluconate”, the so-called “Ajinomoto”, as what most people are familiar with. They also discovered the relationship of when more nitrogen fertilizer was used, the more theanines were accumulated in the tea."

Tying into Hojo's assertion about theanine and umami, the study I read states, "Glutamic acid and theanine are responsible for the umami taste of green tea (Ekborg-Ott et al.,1997; Kaneko et al., 2006)." I do, more or less, trust Hojo and know his background education is in food science (agricultural chemistry with a masters degree in food science). Without a background in the field, I wouldn't know, as I am only beginning a deeper foray into the underlying science of tea. However, at this point, and given how much time Hojo has spent on the ground in various tea farms each year, I am inclined to trust for now his assertions around, at least, in part, modern elevated theanine content in tea being directly related to the use or overuse of nitrogen fertilizers.

Returning to pu-erh, the study I read last night also did a break down of the occurrence of GABA in the various types of teas. It states, "The GABA content was found to be the smallest in pu-erh tea (about 1.9mg/100g) corresponding to the paper by Zhao et al. (2011) who used OPA as derivitization reagent and a fluorescence detector for the determination of GABA in various types of tea."

The study is quite interesting and offers other useful information if anyone is interested.

I bookmarked a couple studies that deal specifically with the questions/questioning put forth at the beginning of the thread as well as others (some noted below). One I set aside to read tonight is titled "Behavioral and molecular evidence for psychotropic effects in l -theanine" and was published in 2011.

Pyronicx wrote:
What I forgot to add is that in one paper they quantified the theanine in different types of tea and the conclusion was that gyokuro contained the most theanine. For me the tea that consistently gives me the strongest psychoactive effects is gyokuro. This, is what lead me to believe that the psychoactivity is most likely caused by the theanine and caffeine. I'll try to obtain some food/pharmaceutical grade L-theanine and see if it has any effect in a safe range (will use same dose range as in the abovementioned study).

the brain works on a glutamic and a gaba-nergic system.. so.. since theanine is a nice glutamate derivative and rather analogous in structure, it definitely does have neurological effects.

tasted crudely purified theanine and caffeine before, purified theanine is sharp savoury with a slight bitter ending, caffeine is sharp bitter and persistant. maybe it would be better to have it diluted instead of tasting the powder.

just a tiny bit of theanine and about ten minutes into tasting you get put into a calm still state of clarity, relaxingly aware. all in all this molecule should be the secret of cha-qi

茶藝-TeaArt08 wrote:Here's the Hojo article I mentioned above in which, at least in this article, theanine content is linked to more intensive application of fertilizers/nitrogen. As is often the case for me with Hojo I find his viewpoints interesting and generally bearing merit, whether I am in full agreement with them or not.:

i dont agree with the statement that theanine rich tea's lack aroma/flavour and needs to be baked.

theanine's all made in the roots of the tea plant.. and depending on specie, age, location, soil type/quality, there can be variations. gushu tea trees has extensive root systems so its ability to sustain and generate theanine is higher. fertilizers are just attempting to ensure the soil doesnt get depleted, but may not be able to change the rate so much as the roots and its symbiotic nitrogen fixing microcosms are still the limitations.

various stages of root developments..

shah82 wrote:Theanine is produced more in shade, less in sun.

actually it is accumulated more in the shade, but is converted to polyphenols in the sun.

kyarazen wrote:theanine's all made in the roots of the tea plant.. and depending on specie, age, location, soil type/quality, there can be variations. gushu tea trees has extensive root systems so its ability to sustain and generate theanine is higher. fertilizers are just attempting to ensure the soil doesnt get depleted, but may not be able to change the rate so much as the roots and its symbiotic nitrogen fixing microcosms are still the limitations. actually it is accumulated more in the shade, but is converted to polyphenols in the sun.

Yes, this is the best summary so far. Theanine is produced in the plant's root system independently of sunlight. Nitrogen fertilizer (and larger root systems, etc.) can increase its production. (There are two nitrogen atoms in each theanine molecule.) It travels to the leaves, where it is one of the ingredients--along with sunlight--used to produce catechins (polyphenols). So if you limit the sun exposure, less catechins are produced and a higher proportion of theanine is preserved. My understanding is that lower brewing temperatures will limit the amount of catechins extracted, thus increasing the proportion of theanine (and other amino acids) in the cup, which provide the umami flavor that Japanese tea production and preparation has been maximizing, as per the hojo article.

I'm glad there are regional differences when it comes to flavor ideals. It would be too bad if increasingly negative perceptions of fertilizer application (and sloppy application of the naturalistic fallacy) led to the disappearance of Japan's unique umami-bombs. By all means, drink organic teas, or those from other countries, but be mindful how your evangelism could destroy something beautiful.

kyarazen wrote:theanine's all made in the roots of the tea plant.. and depending on specie, age, location, soil type/quality, there can be variations. gushu tea trees has extensive root systems so its ability to sustain and generate theanine is higher. fertilizers are just attempting to ensure the soil doesnt get depleted, but may not be able to change the rate so much as the roots and its symbiotic nitrogen fixing microcosms are still the limitations. actually it is accumulated more in the shade, but is converted to polyphenols in the sun.

Yes, this is the best summary so far. Theanine is produced in the plant's root system independently of sunlight. Nitrogen fertilizer (and larger root systems, etc.) can increase its production. (There are two nitrogen atoms in each theanine molecule.) It travels to the leaves, where it is one of the ingredients--along with sunlight--used to produce catechins (polyphenols). So if you limit the sun exposure, less catechins are produced and a higher proportion of theanine is preserved. My understanding is that lower brewing temperatures will limit the amount of catechins extracted, thus increasing the proportion of theanine (and other amino acids) in the cup, which provide the umami flavor that Japanese tea production and preparation has been maximizing, as per the hojo article.

I'm glad there are regional differences when it comes to flavor ideals. It would be too bad if increasingly negative perceptions of fertilizer application (and sloppy application of the naturalistic fallacy) led to the disappearance of Japan's unique umami-bombs. By all means, drink organic teas, or those from other countries, but be mindful how your evangelism could destroy something beautiful.

yeap. lower brewing temperature will limit the amount of polyphenolic catechins that come into the brew.

theanine's pretty polar and not a very big molecule, so it comes out really easily and really quickly in steeps. it should be most apparent in the first two steeps of tea. the taste of it coming from very early spring tea/gyokuro can confuse drinkers into thinking that it is a fluoride taste.

polyphenols are bigger molecular, less ionic although polar in nature, require higher temperatures and longer steeps to push them out into the brew

the tea aesthetic seem to differ between continents, nationalities and diet. there's this interesting chinese tea term called 韵, very important for good chinese teas, but may not be an aesthetic appreciated by many others.

Thanks, Evan. I'll have to check that resource out further when I get back from my travels.

The schematic is still really vague in a number of areas, particularly the formation of catechins and polyphenols -- and particularly because it says that ethylamine is involved, and yet neither of those products contain nitrogren. That's an awfully complicated way to create and use a carbon source, when typically there are better sources.

Also interesting, it says that the theanine is built in the roots and accumulated in the buds. But it doesn't say that the theanine is photolyzed (light) in the buds, it says it is hydrolyzed (water), which means it can happen with or without light. The following step, it claims, uses the ethylamine and light to do other things.